1. Field of the Invention
The present invention is directed to the domain of virtual reality and, more particularly, to processes for creating virtual world models from real world images.
2. Description of the Background
Virtual reality and the concept of virtual worlds has received much attention in the popular press and captured the imagination of the public at large. The ability to navigate through a world seen only on your computer screen, or through a special headset or visor, opens the door for an incredible variety of experiences. Add to the ability to navigate through a virtual environment the capability of picking up objects, or otherwise interacting with objects found in the virtual environment, and the basis for the enthusiasm for the technology becomes readily apparent.
To date, navigable virtual environments with interactive objects embedded therein have been extremely simplistic due to the tremendous amount of modeling that is required to even begin to approximate realistic-looking virtual objects much less a realistic-looking and realistic behaving virtual environment. When one considers size, color, and texture for even a simple object together with how the appearance of the object changes from different vantages, it quickly becomes apparent that the process of creating just virtual objects is a daunting task. As a result, today's virtual environments and objects are either very simplistic looking as they are created using simplistic CAD models, or are extremely expensive, and sometimes both.
One project jointly developed by Apple Computer, Inc., The Massachusetts Institute of Technology, and the University of Regina in Canada called the "Virtual Museum Project" has produced a successful navigable video environment. The virtual museum is a computer-based rendering of a museum which contains various objects of interest. The user can interactively move through the virtual museum and approach individual objects which can be viewed. The objects can be selected and viewed from a variety of perspectives. A complete description of the Virtual Museum Project is found in "The Virtual Museum: Interactive 3D Navigation of a Multi-Media Database," by Miller, et al.
U.S. Pat. No. 5,442,546 entitled Method and Apparatus for Multi-Level Navigable Video Environment issued on Aug. 15, 1995 to Hansen. The Hansen Patent describes a multi-level apparatus to "navigate" an environment consisting of video data. Using a touch-sensitive screen, the user can navigate through the video database of offerings in an interactive manner. Once the viewer has maneuvered to a certain position, a separate data track, for example, data about a particular object, may be viewed.
Although such systems may seem similar to virtual reality systems, they can more accurately be characterized as a video-based hypertext interface to a network of video data. Although it is interactive, it brings up only previously stored scenes in response to user inputs. The systems lack the ability to allow the user to move freely within the environment because of the infinite number of perspectives, i.e. camera angles, that must have been recorded to enable the user to assume such positions. Similarly, images of objects are recorded from predetermined vantages, thereby limiting examination of the objects to just those pre-recorded images.
Apple Computer has developed a software product called Quicktime VR.RTM. which allows a user to navigate within a scene. Scenes can be made from photographs, video stills, or computer renderings. To photograph a Quicktime VR.RTM. scene, the photographer places a camera on a tripod and shoots a series of pictures, turning the camera thirty degrees after each exposure. The images are digitized and input to the Quicktime VR.RTM. software which electronically warps the images, maps the overlapping features, and stitches the images together. Warping makes the stitching possible, and it may appear that images from intermediate viewing positions are generated, but the resultant images are incorrect and contain distortion. In effect, straight lines become curved. When you open a scene with the Quicktime VR.RTM. player, the player corrects for the distortion by unwarping the part of the image being displayed. As you move around, the part of the image being displayed changes so as to keep up with your movements. With respect to objects, objects are composed of a large number of images all taken from a slightly different angle. As you turn the object or tilt it up and down virtually, the Quicktime VR.RTM. software responds to your movements and displays the appropriate images.
The fundamental limitation of these approaches is that they do not have three-dimensional models of the environment. The patent to Hansen and the Apple Quick Time VR software overcome the problems associated with attempting to model complicated objects and environments by simply storing large numbers of images. However, they both suffer from the limitation that what can be viewed by the user is limited to the images that are pre- recorded. Accordingly, the need exists for a method which combines the ability to quickly capture a tremendous amount of detail in the way which photographs can capture detail, but which allows the user to view the objects from an infinite variety of vantage points the way a mathematically-modeled object or environment can be viewed.